:root {
  --green: #548235;
  --bg: #E2EFDA;
  --white: #fff;
}

body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: var(--bg);
  color: #333;
  margin: 0;
  padding-top: 130px; /* phù hợp với header + nav cố định */
}

/* === HEADER === */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background: var(--green);
  color: var(--white);
  text-align: center;
  padding: 18px 0 36px; /* đủ cao cho nút + dòng chào */
  z-index: 999;
  box-sizing: border-box;
}

header h1 {
  margin: 0;
  font-size: 28px;
  font-weight: 700;
}

/* === USER AREA === */
.user-area {
  position: absolute;
  top: 45px; /* hạ thấp xuống dưới tiêu đề */
  right: 25px;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 3px;
  text-align: right;
  color: #fff;
  font-size: 15px;
  font-weight: 500;
}

.user-area a {
  color: #fff;
  text-decoration: none;
  font-weight: 600;
}

.user-area a:hover {
  text-decoration: underline;
}

.user-area p {
  margin: 0;
  font-size: 14px;
  color: #fff;
}






.logout-btn {
  background: var(--white);
  color: var(--green);
  border: none;
  padding: 6px 10px;
  border-radius: 6px;
  font-weight: 600;
  cursor: pointer;
  transition: 0.25s;
}

.logout-btn:hover {
  background: rgb(226,239,218);
}

/* === NAVIGATION === */
nav {
  position: fixed;
  top: 84px; /* căn chuẩn, không đè header, không mất tab */
  width: 100%;
  background: var(--green);
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 24px;
  padding: 10px 0;
  z-index: 998;
  box-sizing: border-box;
}

nav a {
  color: var(--white);
  text-decoration: none;
  font-weight: 600;
  padding: 8px 18px;
  border-radius: 8px;
  transition: 0.25s;
}

nav a:hover, nav a.active {
  background: var(--white);
  color: var(--green);
}

/* === CONTAINER === */
.container {
  max-width: 1000px;
  margin: 0 auto;
  background: #fff;
  padding: 16px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

/* === FEATURES === */
.feature-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 25px;
  margin: 40px auto;
  max-width: 1200px;
  padding: 0 20px;
}

.feature-group {
  flex: 1 1 350px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  padding: 25px;
  transition: transform 0.25s, box-shadow 0.25s;
  border-top: 6px solid var(--green);
}

.feature-group:hover {
  transform: translateY(-6px);
  box-shadow: 0 6px 18px rgba(0,0,0,0.15);
}

.feature-group h3 {
  margin-top: 0;
  font-size: 1.5em;
  color: var(--green);
  border-bottom: 2px solid var(--bg);
  padding-bottom: 8px;
  margin-bottom: 20px;
}

.feature-group ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.feature-group ul li {
  background: rgb(248, 251, 245);
  margin-bottom: 10px;
  padding: 10px 14px;
  border-radius: 6px;
  border-left: 4px solid var(--bg);
  transition: 0.2s;
}

.feature-group ul li:hover {
  background: var(--bg);
  border-left: 4px solid var(--green);
}

.feature-group ul li b {
  color: var(--green);
}

/* Bỏ chấm tròn cho nhóm phím tắt */
.version-box ul .no-dot {
  list-style: none;
  padding-left: 20px;
}

/* === FOOTER === */
footer {
  background: #f1f1f1;
  text-align: center;
  padding: 20px;
  margin-top: 40px;
  font-size: 0.9em;
  color: #555;
}